That isn't to say that a certain amount of "recruiting" doesn't go in to getting a guy to stay for a 4th year, but the situations aren't analagous.

If anything, the better recruiter you are, the worse your retention should be since that elite talent is more likely to jump to the NFL.

In most cases, a player's draft potential has more to do with the decision to stay or go than any efforts from the coaching staff. Michael Floyd didn't stay for his 4th year because BK asked him nicely; he stayed because he didn't receive as I a draft grade as he wanted. And for all the mock drafts that have been going around citing Ronnie Stanley as a high pick, I'm not sure that is how he was evaluated by the actual experts (though perhaps I'm wrong about that).